This can result in serious injury to the fish, and if released in this buoyant condition, the fish may float away and die from exposure to the elements or become an easy target for predators. This defeats the purpose of fishery management laws such as minimum size restrictions and daily bag limits.
Many reef fish have a closed swimbladder, an internal organ filled with gases, mostly oxygen, carbon dioxide, and nitrogen. Swimbladders can expand only so far before they burst. The pressure exerted by these gases is sufficient to push the stomach out the mouth and the intestines out of the anus.
Venting releases these gases from the body cavity, thus eliminating the pressure on the internal organs. If damage is not excessive, the organs will return in place on their own, once the gases are expelled. Venting also will allow the fish to overcome buoyancy problems and swim down to habitat depth, enhancing its immediate survival. Scientific studies have shown that species with large swimbladders such as red grouper, black sea bass, and gag derive immediate benefit from venting.
Your ability to judge which fish should be vented will improve with practice and experience. After reeling in a fish, closely observe its condition. If the fish appears normal, not bloated, and is able to swim down to habitat depth on its own, venting is not necessary.
It is best to vent the fish as quickly as possible with a minimum of handling. Expelling the swimbladder gases will allow the stomach to return to its normal position within a few hours. Hold the fish gently but firmly on its side and insert the venting tool at a degree angle approximately one to two inches back from the base of the pectoral fin. Only insert the tool deep enough to release the gases — do not skewer the fish.
The sound of the escaping gas is audible and deflation is noticeable. Keep a good grip on the venting tool during the entire process, so that an unexpected jerk from the fish does not dislodge the tool and cause injury to others.
This practice is not as efficient in releasing gas from the body cavity and results in additional injury. Return the fish to the water as soon as possible. If necessary, revive it by holding the fish with the head pointed downward and moving the fish back and forth to pass water over the gills until the fish is able to swim unassisted.
Short, second video from Mote Marine Laboratory. Report video problems to us at info flseagrant. A venting tool can be any hollow, sharpened instrument that allows gases to escape. Ice picks and knives are not suitable because simply puncturing the fish is undesirable and can result in a mortal injury. Venting Tools Available Today pdf, k.
It is also possible to make your own venting tool. The modified hypodermic needle pictured is an excellent choice for a fish venting tool. A hollow, sharpened stainless steel cannula mounted on a hollow wooden dowel also works. Cannulas gauge recommended can often be purchased from farm supply and feed stores.
The tool should be cleaned between uses and kept in a safe and accessible place. As with gates vents should be cut "steel safe". Start at the minimum dimension and open the vent up gradually until the optimum molding is achieved.
Too small and the vent will clog up and reduce or eliminate the ability to expel air from the mold cavity; too large and flash may be seen on the moldings. Vents can be placed anywhere along the parting line in particular they should be located in areas that are the last to fill in particular section of the injection mold.
Another option is to use sintered metal inserts, these inserts allow gas to pass into them without clogging up with the polymer. These inserts should only be used as a last resort and only on nonvisual surfaces.
To summarize, inadequate venting many result in various molding failures: Burnt spot Weak and visible weld lines Poor surface finish Poor mechanical properties Incomplete filling, especially in thin sections Irregular dimensions Local corrosion of the mold cavity surface. Compression Molding and Extrusion The process of compression molding may be simply described by reference like two-piece mold provides a cavity in the shape of the desired molded article.
The mold is heated, and an appropriate amount Plastic Injection Molding Aco Mold is a good reputation plastic injection mold manufacturer and custom molding company in China, we are always ready to offer best services to your company, provide cheap and high quality
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